How much sleep do you need? There are over seven billion propers answers to that question. Some people function beautifully on three. Quite a few, particularly ill folk, need eight or nine hours or more. To rebuild the body takes time. It takes different amount of sleeping rest for different people.
But when the American Association of Sleep Medicine was tasked to give a “national” answer, they came up with seven to nine hours of sleep as a suggested guideline. And more recent studies argue that seven hours may be a sweet spot for health, as well as performance.
A recent study out of Amsterdam by Femke Rutters et al. looked at 788 healthy men and women between the ages of 30 and 60. They were researching the relationship between insulin and potential diabetes and heart disease. They also looked at sleep.
For the men – but not the women – sleeping more than seven hours, or less than seven hours, decreased insulin sensitivity and other factors related to eventual mature onset diabetes. Lots of studies have shown sleep disruption or partial deprivation disrupts glucose metabolism. But the seven hour figure was pretty robust here, and has appeared in other studies, where it appeared true for men and women. Glucose physiology is critical to weight control. No real surprise – it’s the main fuel source in the body.
Does That Mean Seven Hours in Bed Is the Guideline?
No. What was measured was an indirect marker for sleep, not sleep time. Even perfect sleepers manage at best 95-98% of their time in bed actually asleep. So if you’re aiming for seven hours sleep to see if this makes you feel more alert and productive, you probably need to put in seven and half or seven and three quarter hours actual bed time. Sleep efficiency – time asleep divided by time in bed –decreases gradually with age. Many physically healthy folks over 70 have a sleep efficiency of 85% or less.
How Much Sleep Are People Getting?
Total sleep time variability across the globe does not vary that much in industrialized countries. But working Americans are typically getting six and a half to six and three quarters hours of sleep a night. Quite a few feel they function quite well on that amount. However, for many this means prolonged partial sleep deprivation over years and decades. Overall, that produces a toll on the total population. The most obvious manifestations will be subtle degradation in productivity, more insulin insensitivity and diabetes, and greater weight gain.
When Should I Get Sleep?
At night. Humans are daytime animals. We perform sleep best at night. The quarter of the American population that does shift work knows this very well.
What Can Shift Workers Do?
There is a whole industry engaged in trying to get shift workers optimal sleep and rest. Disrupting biological clocks also disrupts people’s health. Some of the adaptations shift workers use are naps on the job (which sometimes get them fired); naps at biologically clock appropriate times on both working and non-working days; and long, recovery sleeping periods on days off. Even with the best adaptations, shift work worsens long term health.
What If I Need Seven Hours or More Sleep a Day, and I Can’t Possibly Get Those Hours at Night?
A 24/7 society is better suited for machines than people. Our work/socialize all the time pattern has become so pervasive that many people start viewing themselves as machines. That can really hurt your health, especially your ability to regenerate yourself. One common adaptation people use is short naps. Naps as short as six minutes have been shown to improve alertness and productivity. Naps between 10-30 minutes appear to disrupt nighttime sleep less than longer naps.
Another major adaptation engages techniques to improve sleep efficiency, so that you get as much sleep as you can during your time in bed. A cool, calm, comforting sleep environment helps. Walking in the morning, in light, can also prove useful. There is something about morning light that improves mood, mental sharpness, and ability to sleep. Some of this probably comes from light resetting internal biological clocks. Another factor to consider is physical activity and exercise of almost every type. People who are fit usually experience greater sleep efficiency. They also may experience more deep sleep and REM sleep, with their special capacities to aid learning and bodily regeneration.
Sleep need is uniquely biological to every human being. Some of us only a few hours of sleep each night, but that’s a small minority. It looks like the national recommendation for seven hours of sleep – not time in bed, but sleep – may be a helpful guideline for many adults who want to live long and not become diabetic and overweight. Getting that amount of sleep means giving more time than 7 hours to time in bed; having pretty tight biological clocks, aided by going to bed and getting up at regular hours; and becoming reasonably fit.
What you do is what you become. Sleep is like food. If you get the right amount, in the best ways for your body, you function better.